Isomers of N,N{40 -bis-{8 (1-formamido-2,2,2-trichloro)-ethyl{9 -piperazine and method of isolating the same

ABSTRACT

Isomers and isomeric mixtures of N,N&#39;&#39;-bis-(1-formamido-2,2,2trichloro-ethyl)-piperazine, and a method of isolating such isomers and isomeric mixtures by extracting conventionally prepared N,N&#39;&#39;-bis-((1-formamido-2,2,2-trichloro)-ethyl)piperazine, which contains about 50% by weight of the more soluble isomer, with a solvent or solvent mixture in which the solubility ratio of the more soluble isomer to the less soluble isomer is at least about 3:2, isolating the extracted substance and optionally further purifying the isolated substance by conventional purification procedures, such as recrystallization or chromatography; the isomers and isomeric mixtures thus obtained are useful as agricultural fungicides.

United States Patent [1 1 0st et al.

[4 1 Oct. 14, 1975 ISOMERS OF N,N -BIS- l -FORMAM[DO-2,2,2-TRICHLORO)-ETHYL]-PIPERAZINE AND METHOD OF ISOLATING THE SAME [75]Inventors: Walter 0st, Bingen; Klaus Thomas, Gau-Algesheim; EkkehardAmadori, Darmstadt-Arheilgen; Rolf Darskus, Gau-Algesheim, all ofGermany [73] Assignee: Celamerck Gmbl-l & Co. KG,

lngelheim am Rhein, Germany 22 Filed: Feb. 11, 1974 21 Appl. No.:441,010

[30] Foreign Application Priority Data Feb. l0, 1973 Germany 2306623Oct. 15, 1973 Germany 2351707 Dec. 21, 1973 Germany 2363729 [52] US. Cl260/268 R; 424/250 [51] Int. Cl. C07D 295/12 [58] Field of Search260/268 R [56] References Cited UNITED STATES PATENTS 3,696,106 10/1972Ost et al 260/268 R Primary Examiner-Donald G. Daus AssistantExaminer.lose Tovar Attorney, Agent, or FirmHammond & Littell lsomersand isomeric mixtures of N,N-bis-(lformamido-2,2,2-trichloro-ethyl)-piperazine, and a method of isolatingsuch isomers and isomeric mixtures by extracting conventionally preparedN,N'-bisl-formamido-2,2,2-trichloro )-ethyl] -piperazine, which containsabout 50% by weight of the more soluble isomer, with a solvent orsolvent mixture in which the solubility ratio of the more soluble isomerto the less soluble isomer is at least about 3:2, isolating theextracted substance and optionally further purifying the isolatedsubstance by conventional purification procedures, such asrecrystallization or chromatography; the isomers and isomeric mixturesthus obtained are useful as agricultural fungicides.

5 Claims, 2 Drawing Figures ISOMER I FIG.I

ISOMERIII FIG.2

ISOMERS OF N,N'-BIS-[( l-FORMAMIDO-2,2,2-TRICI-ILORO)- ETHYL1-PIPERAZINEAND METHOD OF ISOLATING THE SAME This invention relates to novel isomersand isomeric mixtures of N,N'-bis-[(l formamido-2,2,2-trichloro)- ethyl]-piperazine and a method of isolating these isomers and isomericmixtures from conventionally prepared N,N'-bis-[(l-formamido-2,2,2-trichloro)-ethyl piperazine.

THE PRIOR ART US. Pat. No. 3,696,106 disclosesN,N'-bis-[(lformamido-2,2,2-trichloro)-ethyl]-piperazine and a method ofpreparing the same, as well as the broadspectrum fungicidal propertiesof this compound against various phytopathogenic fungi.

THE INVENTION We have discovered that N,N'-bis-[(l-formamido-2,2,2-trichloro)-ethyl]-piperazine (hereinafter sometimes referred to byits generic name triforine) obtained by the process described in U.S.Pat. No. 3,696,106 actually consists of two components which, by virtueof their different solubilities in certain solvents, can be separatedand isolated. With respect to their significant properties for practicalemployment as fungicides, these two components exhibit considerabledifferences; and, in addition to differences in solubility, the twocomponents also exhibit differences in other physical-chemicalproperties, such as their nuclear molecular resonance (NMR) spectra andR values.

The triforine molecule comprises two asymmetric carbon atoms withidentical substitution, so that in the synthesis of triforine by theprior art process 50% of D,L-triforine (meso-form) and 50% of racemictriforine (25% L,L-triforine and 25% D,D-triforine) are formed.

The above-mentioned components of differing solubility are, on the onehand, the racemate designated in the following by I and, on the otherhand, the meso-form designated in the following by II.

Of special importance for practical purposes is that I has a strongerfungitoxic action upon phytopathogenic fungi than either II or theisomeric mixture obtained pursuant to the prior art process.

Surprisingly, mixtures of I and II, wherein the content of I has beenenriched to about 60%, also show a considerably stronger fungicidalaction than expected. (The percentages here and in the following arepercentages by weight, unless otherwise indicated).

Therefore, it is an object of the present invention to provide anindustrially feasible process for the production of fungicidally activetriforine isomers or isomer mixtures containing at least 60% by weightof I.

In the industrial scale production of triforine from pi- ,perazine andtetrachloroethyl-formamide a mixture of isomers I and II is isolated inthe approximate weightratio of 45 55. We have discovered that, when thismixture is treated with a solvent or solvent mixture in which thesolubility ratio of isomer I to isomer II is at least about 3:2. anenrichment in the concentration of I or II is achieved which leads,depending upon the type and quantity of the solvent as well as sometimesalso the chosen temperature, to the isolation of the respective pureisomers.

Solubility weight Solvent unit volume (w/v) Ratio at 22CSolub.I/Solub.|l I II Methanol 2.8 0.6 4.7 Cyclohexanone 3.2 1.4 2.3acetone 5.8 1.1 5.3 Tetrahydrofuran [0.4 2.0 5.2 N-methylpyrrolidone22.5 28 0.8 Dimethylformamide 42 15.5 2.7

(DMF) Aqueous acetone with a water content of 5 to 20% has proved to beespecially suitable for the separation of the isomers. If, for example,aqueous 90% acetone is used, for the extraction of a mixture of about50% I and II the great difference in solubilities of I and II in thisaqueous mixture. produces in the liquid phase a strong enrichment of Iwhich is more soluble therein. By means of continuous or repeatedextraction, it is possible without difficulties to ultimately obtain aresidue consisting exclusively of the more difficultly soluble meso-formII. By evaporation of the extracts, triforine fractions stronglyenriched with racemate I are obtained, which by suitable furtherpurification, such as recrystallization from acetonitrile, may beconverted into pure racemate I.

A further, especially preferred, embodiment of the isomer enrichmentprocedure consists of treating technical grade triforine with a quantityof dimethylformamide which is insufficient for a complete dissolution ofthe compound.

Although the solubility ratio of I and II in DMF of 2.7 is relativelysmall, the biologically more active form I may surprisingly be separatedalmost completely from a 1:1-mixture by a single extraction of theisomer mixture with DMF. This method has several decisive advantages incomparison with other enrichment processes:

1. Due to the good solubilityof I in DMF, a relatively little solvent isneeded for extraction.

2. The yield of extraction of l is almost quantitative, so that thereoccurs hardly any loss in the desired biologically more active form.

3. Highly concentrated solutions with a content of up to more than 40%w/v of triforine strongly enriched with I are obtained. Without furtherisolation of the racemate I, these solutions may be used as such for theproduction of liquid triforine concentrates, since DMF is an especiallysuitable solvent for such liquid compositions.

4. If it is necessary to isolate the active ingredient dissolved in DMF,the isomer mixture'enriched with I may easily be quantitativelyprecipitated by pouring the DMF-solution into water. Alternatively, theDMF may be distilled off in vacuo.

The separation processes described above lead, in

general, to a residue of almost pure form II; however,

the isomer I obtained from the solutions always contains about'lO to 30%of the isomer II, as illustratedby the following schematic separationexample:

500 gm of triforine; nu 45355 extraction with 500 ml of DMF residuesolution 240 gm 650ml, containing 260 gm of Hi 5:95 triforine 40% w/vRatio of isomers in the dissolved triforine: lzll 82:18

A further enrichment or purification of isomer I is readily feasible bya second purification process, e. g. by a second extraction or byrecrystallization, for instance from acetonitrile. It has been noted,however, that it is of advantage for the production of fungicidalcomposi tions, especially of liquid formulations, to use a mixture whichstill contains a certain proportion of isomer II. Thus, upon dilution ofthe solution concentrate with water to the desired applicationconcentration, sprays are obtained which are especially stable and donot form any sediment, even after standing for a prolonged time. If pureisomer I is used for production of-these solution-concentrates, however,it occasionally happens, especially if the hardness of water is verylow, that the spray forms considerable. quantities of active ingredientsediment after prolonged storage, which may, under certain circumstancescause difficulties whenit is used for plant protection.

Therefore, it is a further object of the present invention to providefungicidal agents or compositions which are characterized by especiallyhigh activity against phytopathogenic fungi, and in case of liquid formulations yield spray solutions with good stability when diluted withwater.

4 The active ingredients used in'accordance with the inven'tion'generally contain, besides the isomer II at least about of the isomer I;The content of l amounts preferably to to 97%. Particularly preferredare mixtures of isomers containing to 95%,

especially m 0f the isomer I.

Pursuantto a preferred embodiment of the invention, therefore, thetechnical gradmixture of isomers is treated with such quantities ofdimethylformamide that extracts are obtained which contain dissolvedtherein about 25 to 42% of triforine with an isomer-ratio of I II fromabout 60:40 to about 90:10. These extracts may be converted by means ofsuitable additives, such as additional'solvents, emulsifiers andoptionally defoamers, directly into liquid formulations (solutionconcentrates, emulsion concentrates) with the desired content of activeingredient.

A separation of the triforine racemate 1 into its two optically activecomponents is not possible by conventional methods. The basicity of thetriforine racemate, for example, is so low that stable salts withoptically active'acids cannot be prepared. Also, tests for fractionalcrystallization of the triforine racemate with optically active solventsare severely limited because of the low solubility of triforine.

Therefore, it is a further object of the present invention to provide aprocess for isolation of levo-rotatory triforine in optically pureorenriched form. We have discovered that levo-rotatory triforine ischaracterized by an especially strong fungicidal action.

The following schematic synthesis flow sheet illustrates the preparationof (),()-triforine in accordance with the present invention:

NH-CHO H -r.(+)- moo-choir) First, piperazine is reacted only at onenitrogen atom with (+),(-)-l,2,2,2-tetrachloroethyl formamide to form(+),()-N-[( 1-formamido-2,2,2-trichl0r0 ethyl]-piperazine (hereinafterreferred to as monotriforine"). This compound possesses only oneasymmetric center and still exhibits, due to the unsubstituted secondaryamino group of the piperazine moiety, sufficient basicity for theformation of diastereomeric salts with optically active auxiliary acids.In principle, any desired optically active acid, such as L(+)-lacticacid, D(+)-camphoric acid, D(+)-a-bromocamphor-1rsulfonic acid,()-0,0'-dibenzoyl-tartaric acid, (+)-mandelic acid, ()-mandelic acid,L()-malic acid or L-()--pyrrolidinone 2 carboxylic acid may be used forproduction of diastereomeric salts of monotriforine. However, especiallysuitable as a salt-forming auxiliary acid is L(+)-tartaric acid, becausewe have fract.extraction/fract.crystallization found that the twodiastereomeric hydrogen tartrates of mono-triforine may be separated,based on their different tendencies toward solvate formation andstrongly differing solubilities of the solvates, with excellent yieldsand without great purification expenditures.

If the mixture of diastereomeric hydrogen tartrates is dissolved inwater, the (-)-mono-triforine-hydrogen tartrate crystallizes out aspentahydrate with a yield of more than 90% and with an optical purity of98%. By recrystallization from water, the optical purity can beincreased to above 99.5%. p

The aqueous filtrate contains (+)-mono-triforinehydrogen tartrate, whichis very freely soluble in water. After distilling off the water andtreating the residue with 96% ethanol, the (+)-mono-triforine-hydrogentartrate is obtained as crystalline ethanol solvate with over yield andan optical purity of over 99%.

The separated diastereomeric mono-triforinehydrogen tartrates may beconverted by treatment with alkali, in aqueous solution, into theoptically pure bases with specific rotations of 63.0 and +62.6,respectively, Here, too, further purification is not required.

In the next synthesis step, optically pure ()-monotriforine is reactedagain with (+),()-l ,2,2,2- tetrachloroethyl-formamide. In this manner amixture consisting of 50% meso-triforine and 50% triforine is obtained.Correspondingly, from (+)-monotriforine a mixture of 50% meso-triforineand 50% (+),(+)-triforine is formed.

Separation of these mixtures into the corresponding isomers is effectedby fractional crystallization or fractional extraction. In this mannerthe 2- to 6-fold greater solubility of levo-rotatory and dextro-rotatorytriforine, respectively, compared to meso-triforine is exploited.Especially suitable as solvents are methanol, acetone with up to wateradded, tetrahydrofuran, acetonitrile or dimethylformamide. An enrichmentin triforine is possible, for example, by extraction of the mixture oflevorotatory triforine and meso-triforine with aqueous 90% acetone,boiling methanol, tetrahydrofuran or dimethylformamide (DMF). Here, theextraction with a quantity of DMF insufficient for a completedissolution of the mixture of isomers represents an especially preferredembodiment of the enrichment in (),()-triforine, because DMF possesses agood dissolving capability for levo-rotatory triforine and, moreover,these solutions may be used directly for production of highly effectivecompositions for plant protection. If it is desired to isolate enrichedlevo-rotatory triforine as a solid material, the substance may beprecipitated by pouring the DMF solution into water, or by distillingoff the solvent in vacuo.

In order to isolate the optically pure isomers, it is advantageous tofirst separate the major amount of the meso-form by selectiveextraction, and then recrystallize the enriched'optically active productcontaining about 65 to 90% of Ievo-rotatory triforine. Especiallysuitable as solvents for recrystallization are methanol andacetonitrile.

For isolation of small quantities of the pure isomers, mechanicalseparation methods may be applied as well, because under certainconditions the meso-form and optically active triforine separate out indifferent, welldefined forms of crystals. Upon slow crystallization of amixture of the meso-form and (),()-triforine from acetonitrile,meso-triforine crystallizes out, for example, in the form of clear,colorless prisms, while levorotatory triforine separates out in the formof bundles of colorless needles.

It is of special significance for the practice of plant protection, thatthe three triforine isomers exhibit very different fungitoxic actionsupon various phytopathogenie fungi. Biological examination of the threeisomers showed a decrease in fungitoxic action in the sequence(-),(.)-triforine I meso-triforine (+),(+)-triforine.

Consequently, by far the biologically most active form is levo-rotatorytriforine. Thus, it has become possible by virtue of the pro'cess ofpreparation of or enrichment in (),()-triforine according to the instantinvention to make available for plant protection an active ingredientwhich considerably'surpasses the triforine isomer mixture in itseffectiveness against phytopathogenic fungi.

For economic reasons it is of advantage not to use levo-rotatorytriforine in its optically pure form for production of plant-protectingcompositions, but as a mixture enriched to 45 -95%.

While normal technical grade triforine contains only about 25% of thelevo-rotatory isomer, the procedure pursuant to the present inventiondescribed in Example 3d below already yields, without furtherenrichment, a product containing about 50% (),(-)-triforine. By means ofa subsequent selective extraction procedure pursuant to Example 4 below,a triforine solution is obtained wherein the dissolved triforinecontains about of the (),()-form. Thus, the expensive fractionalcrystallization procedure is required only if optically completely pure(),()-triforine is to be produced, which is not essential forplant-protecting purposes.

Liquid formulations with levo-rotatory triforineenriched activeingredient content are preferably produced by diluting a high-percentageactive ingredient solution in a suitable solvent, preferably in DMF,obtained pursuant to Example 4 to the desired active ingredientconcentration with additives, such as emulsifiers, optionally furthersolvent and de-foamers.

Solid formulations with pure or enriched triforine content, such assuspension powders, granulates and dusting powders, are prepared inconventional manner by adding the conventional excipients and carriers.

- The isomer II which is obtained upon separation of isomers I and II orduring the production of levorotatory triforine is, as alreadyexplained, less desirable for fungus control.

The present invention also solves the further problem to convertmeso-triforine (II) by racemization into the biologically more activeracemic form (I).

In solid form, I and II are stable under normal conditions; afterseveral years storage at room temperature no isomerization could benoted.

In solutions, too, there is no isomerization at room temperature andbelow.

We have now found that II can be isomerized into I in solution atelevated temperature. Since the equilibrium ratio between I and II isabout 1:1, the conversion in one step may lead to a maximal yield of50%. By repetition of the isomerization process with the mesoform, whichis always re-obtained after separation of the racemate, a practicallycomplete conversion may gradually be effected.

The isomerization may advantageously be carried out as a continuousprocess by removing the racemate continuously from the reactionsolution. Due to the consid- 1 erably higher solubility of the racematein comparison to the mesoform, this continuous process is relativelyeasily performable on a technical scale in most of the solvents suitablefor isomerization.

Especially suitableas solvents for isomerization are dimethylformamide,N-methylpyrrolidone, dimethylacetamide, hexamethyl phosphoric acidtriamide, caprolactam, phenol or mixtures of these solvents. Theadvantage of the above solvents is their good dissolving power for thetriforine isomers. However, other solvents, such as dimethylsulfoxide,tetrahydrofuran, cyclohexanone, butyrolactone, acetone, acetonitrile ormethanol may be used, either by themselves or in an admixture with othersolvents. The addition of water recrystallized from 1700 ml ofacetonitrile. 70 gm of almost pure isomer I were obtained, which wererecrystallized once more from 1200 ml of acetonitrile. In this way, 48gm of analytically pure I were obtained in the form of well-defined,glass-clear colorless crystals.

Decomp. point 179C C calc. 27.61% found 27.98% R -value 0.51 H 3.24%3.35% (silicagel: Cl 48.19% 48.98% chloroform/methylglycol 9 1) N 12.88%12.69%

vents, elevated temperatures may also cause losses of active ingredientdue to decomposition. The most favorable temperature range forisomerization is about 40 to 100C, and the preferred range is from 60 to100C.

The isomerized triforine solutions may be purified by pouring them intowater. Possibly formed degradation For isolation of the pure isomer II,the 67 gm of filter residue of the fourth extraction were boiled twicewith 350 ml each of acetonitrile. 63 gm of analytically pure II wereobtained. A 0.5 gm-sample was recrystallized from 75 ml of acetonitrile.The obtained 0.35 gm of II did not differ in elemental analysis,decomposition point, thin-layer chromatogram, NMR and IR- products areeasily soluble in water, while the active inspectrum f th in q ntityextracted by boiling,

Decom. point 181C C calc. 27.61% found 27.79% R value 0.57 H 3.24% 3.50%(silicagel; Cl 48.91% 48.70% chloroform/methylglycol 9 1) N 12.88%12.64%

NMR-spectra (100 megacycle-spectrum, solvent DMSO-d temperature 28C).

gredient, due to its low water-solubility, precipitates quantitativelyfrom water. By washing the crystallizate with water and drying it, theisomer mixture is obtained which may either be used directly for theproduction of plant-protection compositions or processed furtherpursuant to the process described above.

If isomerization conditions are chosen under which there is practicallyno degradation of the active triforine ingredient, the reactionsolutions may be pro- "cessed into plant-protecting compositions,especially liquid formulations, without isolating the active triforineingredient.

The following examples further illustrate the present invention and willenable others skilled in the art to understand it more completely. Itshould be understood, however, that the invention is not limited solelyto the particular examples given below.

EXAMPLE I 200 gm of finely milled triforine (isomer ratio I: II 5048:52) were stirred with 1000 ml of aqueous 90% acetone for one hour at22C. The undissolved triforine residue was filtered off and dried, andthe acetone extract was evaporated in vacuo, whereby 140 gm of filterresidue and 60 gm of evaporation residue were ob- 55 tained. The filterresidue was treated again with 5 times its amount (700 ml) of aqueous90% acetone like before, and the separation process was repeated twicewith each of the residues:

Amount used of filter evaporation triforine acetone residue residue 1stextraction 200 gm 1000 ml 140 gm 60 gm 2nd extraction 140 gm 700 ml 95gm 45 gm 3rd extraction 95 gm 475 ml 75 gm 20 gm 4th extraction 75 gm375 ml 67 gm 8 gm For further purification, the evaporation residues ofthe first and the second extractions (total 105 gm) were In the case ofI, the methylene protons of the piperazine ring produced a symmetricalmultiplet of 2.62 to 3.00 ppM (6), while in the case of II, a value of2.60 to 3.02 ppM (8) was found.

The corresponding sections of the NMR-spectra are shown in the attacheddrawings, where FIG. 1 is the NMR-spectrum for I and FIG. 2 is theNMR-spectrum for II.

EXAMPLE 2 v 1000 gm of technical grade, finely milled triforine (contentof pure triforine: 99%; ration of isomers I II 47:53) were suspended in1000 ml of dimethylformamide (DMF). The suspension was stirred for onehour at 22C, and was then vacuum-filtered. The filter cake was washedtwice with 50 ml each of DMF. A total of 1220 ml of filtrate with adensity of 1.1 1 were obtained.

Quantitative analysis showed that the obtained DMF solution contained atotal of 522 gm of active triforine on the total quantity dissolved inDMF) of actllfe triforine substance with the same ratio of I II WlllEllwas l 1 present in the DMF solution'(here l Il 84;: 16), was obtained. rThe extraction'residue was treated with 3 liters ofwater,vacuum-filtered, washed with .water until free from DMF and dried at80C. 469 gm of residue with ,a ratio of isomers ofl I1 6 94 wereobtained.

7 EXAMPLE 3 a. (+),()-N-[(1-Formamido-2,2,2-trichloro)-ethyl]-vpiperazine A solution of 220 gm (1.04 mol) of (+),()-1,2,2,2-tetrachloroethyl-formamide in 400' rnlof acetone and a solution of 140gm (1.03 mol) of "sodium acetate trihydrate in 200 ml of water weresimultaneously added dropwise to a solution of 86.gm (1 mol) ofpiperazine in a mixture of 80 ml of 12.5 N hydrochloric acid (1 mol) of800ml of water, while stirring. The initially clear solution becamegradually turbid, and a colorless, viscous precipitate formed. Afterstirring for 30 minutes at 35C, a solution of 170 ml of 6N sodiumhydroxide (1.02 mol) was added at that temperature. The acetone wasdistilled off in vacuo at room temperature, and the precipitated crys-'tals of N,N'-bis-[(1-formamido-2,2,2-trichloro)-etnyl]- piperazine werecollected by vacuum filtration (36.5

gm). The aqueous filtrate was saturated with about 500 v N-1formamido-2,2,2-trichloro)-ehtyl1 piperazine 250 gm (0.5 mol) of()-N-[(l-formamido-2,2,2- trichloro)-ethyll-piperazineL(+)-hydrogentartrate pentahydrate were suspended in 1500 ml of water.While cooling and stirring the suspension, 490 ml of 2N sodium hydroxide(0.98 mol) were added dropwise at A solution of 63.3 gm (0.3 mol) of(+),()-1,2,2,2-

Tetrachloroethyl-formamide in 300 ml of -ethylacetate(analytically pure)was added dropwise at gm of sodium chloride, whereby the hydrochlorideof the compound named in the heading separated out in crystallineform.The crystals were collected by vacuum filtration and dissolved in 1000ml of water, a small amount of insoluble matter was filtered off, and

while cooling, the filtrate wasadmixed with 170 ml of No furtherpurification effect was achieved by recrysv tallization fromethylacetate.

. b. ()-N-[( 1-Form amido-2,2,2-trichloro)-ethyl]- piperazineL(+)-hydrogen tartratepentahydrate 156' gm (0.6 mol) of )-N-[(l-formamido- 2,2,2-trichloro)-ethyl]-piperazine and 93' gm (0.62 mol)of L(+)-tartaric acid were dissolved'at 3040C lowed to stand for about24 hours at .+5C. Thereafter,- the supernatant liquid was carefullydecanted from the large, clear crystals, and the crystallizate waswashed twice with a little ice water. The residue was air-dried at roomtemperature. 138.9 gm (92.5% of theory) of ()-N-(1-formamido-2,2,2-trichloroethyl)piperazine L(+)-hydrogen ztartratepentahydrate were obtained. [01],, 21.7 (water; c 6) (optical purity98.1%).

Upon recrystallizing the product once from 6 parts of water at no morethan 50C the compound was obtained with an optical purity of 100%;[a],,: 24. 8 (water; 0 6). C H Cl N O C 1-l O 5 H O +4C over a period ofabout 20 minutes to a suspension of 78.2 gm (0.03 mol) of()-N-[(1-formamido-2,2,2-

trichloro)-ethyl]piperazine in a mixture of 30.3 gm (0.3 mol) oftriethylamine and 300 ml of ethylacetate (analytically pure), whilestirring.v The resulting mixture was stirred for one hour more at nomorethan 5C, and the colorless crystal mixture was collected by vacuumfiltration and washed with 100 ml of ethylacetate.

.The dried, pulverized residue was treated with;600 ml of water,vacuum-filtered and washed with water until free of chloride. Theresulting mixture of mesotriforine and levo.-rotatory triforine wasdried in vacuo at no more than 60C. 1 15 gm of triforine A) wereobtained; m.p. 175176C (decomp); [011 3 -40.4 (DMF; c 6) ratio ofmeso-triforine: levo-rotatory triforine =51 .5:48.5).

in 800 ml ofdeionized water,and the solutionwas al- The combined ethylacetate filtrates were evaporated invacuo below 40C, and the semi-solidresidue was shaken with a mixture of 200 ml of water and 200 ml ofmethylene chloride. The methylene chloride phase was separated andallowed to stand for about 20 hours at 0 10C. The. triforine.precipitate formed thereby was collected by vacuum filtration, washedwith water and methylenchjloride, and dried below 60C.

Another 6.8 gm of triforine, m.p. 173-175C (dec 6) (ratio ofmeso-triforine levo-rotatory triforine 12:88). Total yield of triforine:121.8 gm =,93.4% of theory. 1

' 1 e. Separation of (+),()-N,N'-bis-[( 1-formamido-2,2;2-trichloro)-ethyl]-piperazine and (),()-N,N-bis-[(1-formamido-2-,2,2-trichloro)-ethyl]-piperazine liquor was carefully decanted from the crystals whichhad formed, and the crystals were washed twice with acetonitrile.yielding bundles of colorless needles, mp 173-175C. (decomp.); [011+82.2 (DMF; c 6); ratio of levo-rotatory triforine meso-triforine 98.51.5). Upon one more recrystallization from acetoni trile, levorotatorytriforine was obtained practically without any meso-form impurity. [M83.2 (DMF; c 6; optical purity 99%).

[1. Separation of major amount of isomer mixture 10 114 gm of themixture of meso-triforine and levorotatory triforine obtained in Example3d A; ratio of isomers 51.5 48.5) were finely pulverized and refluxedfor 5 minutes, while stirring, with 580 ml of analytically puremethanol. The resulting suspension was vacuum-filtered while still hoton a preheated suction filter (filter cake =11 A). The filtrate wasdiluted to 580 ml of methanol (analytically pure), heated again to theboiling point, filtered while hot to remove a small amount ofundissolved material, and evaporated into vacuo.

59 gm of a crystalline residue II B) were obtained. [01], 63.8 DMF; c 6)(ratio of levo-rotatory triforine meso-triforine 76.5 23.5).

58 gm of II B were dissolved in 700 ml of boiling ana- 25 lytically puremethanol. The warm solution was seeded with meso-triforine (preparationsee below) and allowed to stand for 24 hours at room temperature. Thesupernatant methanol solution was decanted from the separated crystalswhich consisted mostly of mesotriforine, and the solvent was distilledoff in vacuo.

35.9 gm of already highly enriched ()-triforine remained (=11 C). [01],,74.0 (DMF; c 6) (ratio of levo-rotatory triforine meso-triforine 89 11).

30 gm of pulverized II C were dissolved in 600 ml of boilingacetonitrile, the solution was seeded with seed crystals of pure()-triforine obtained in Example 3e)l, and the mixture was allowed tostand for 72 hours at room temperature. The crystallizate was collectedby vacuum filtration, washed with acetonitrile and purified twice morein the same way by recrystallization from acetonitrile. 8.6 gm of pure()-triforine of m.p. l76177C (decomp.) were obtained. [04],, 83.0C (DMF;c 6) (optical purity 99%). R value 0.50 (chloroform/methylglycol 9 1 onsilicagel) Analysis: C H Cl N O Calculated: 27.60% C Found: 27.72%C3.24% H 3.50%H 12.88% N 12.75%N 48.91% Cl 49.15%C1 Analysis: C H Cl N,O-

Calculated: 27.60% C Found: 27.77%C 3.24% H 3.38%H 12.88% N 12.61%N48.91% Cl 48.75%Cl Analogously, dextro-rotatory triforine was obtainedfrom (l )-N-( l-formamido-2,2,2-trichloroethy1 piperazine andD,L-1,2,2,2-tetrachloroethylformamide. First, the mixture of isomerswith a specific rotationof +38.4 (in DMF) was obtained, and from thisisomer mixture pure (+)-N, N'-bis-[(lformamido-2,2,2-trichloro)-ethyl]-piperazine, m. p. l74l75C (decomp.),[04],, +83.7 (DMF, c 6), optical purity 99.5%, R value 0.50(chloroform/methylglycol 9:1 on silicagel), was isolated by fractionalcrystallization.

EXAMPLE 4 Enrichment of()-N,N'-bis-(1-formamido-2,2,2-trichloro)-ethyl]- piperazine 130 gm (0.3mol) of a finely pulverized mixture of (-)-triforine and meso-triforine([01],, =40.2; ratio of levo-rotatory triforine meso-triforine 48 z 52),prepared according to Example 3d, were stirred with 150 ml ofdimethylformamide for two hours at 40C and subsequently for two hours at+20C. Thereafter, the resulting suspension was vacuum-filtered, and thefilter cake washed twice with 10 ml each of DMF. The residue wassuspended in 200 ml of water, the suspension was vacuum-filtered, andthe filter cake was washed with water and dried below C. 53.1 gm of asubstance having a m.p. of 176178C (decomp.) were obtained. [04],, -4.7(DMF, c 6) (ratio of levo-rotatory triforine meso-triforine 5.5 94.5).

The combined DMF-filtrates amounting to a total of 188 ml contained 76gm 40.5% w/v) of triforine, made up of 78.5% levo-rotatory triforine and21.5% meso-triforine. Yield of extraction of ()-triforine 96% of theory.(The ratio of isomers was determined densitometrically). The()-triforine-enriched DMF solution can be processed directly into aliquid plant-protecting composition (see Example 5).

In order to isolate the levo-rotatory triforineenriched mixture as asolid substance, 94 ml of the DMF solution were stirred into 1500 ml ofcold water. After stirring for 15 minutes, the precipitated substancewas collected by vacuum-filtration, washed with water and dried below60C. 37.2 gm of triforine, m.'p. 174-176C (decomp.), were obtained;[11],, 65.2 (DMF; c 6), ratio of levo-rotatory triforine mesotriforin 7822.

I EXAMPLE 5 Solution Concentrate 37.1 ml of the 40.5% triforine solutionin DMF enriched with levo-rotatory triforine obtained in Example 4 wereadmixed with 10 gm of the isopropylamine salt of the dodecylbenzenesulfonic acid and 3 gm of isohexadecanol, and the mixture was dilutedwith N-methyl-pyrrolidine to ml. A liquid concentrate was obtained witha 15% w/v content of triforine (ratio of ()-triforine meso-triforine78.5 21.5). The ratio of isomers remained unchanged after 4 months ofshelf storage at 22'28C. By dilution with "water, theliquid concentratemay be adjusted to the desired concentration for use as a fungicidalplant spray.

Sodium tetrapropylene benzenesulfonate 1% 20 gm of meso-triforine wereheated to 60C in a mixture of 43 gm of dimethylformamide and 43 gm. ofN-methylpyrrolidone (total volume of the-solution at room temperature:100 ml). The ratio of isomers after various periods of time, as well asthe yield of racemates is shown in the following table: 1

lsomerization Ratio of Total active Yield of time (60C) isomersingredient racemate racemate: content of meso-form solution days 0 10020.0 gm 9 days 32: 68 19.0 gm 6.1 gm 15 days 38: 62 18.2 gm 6.9 gm 30days 49: 51 16.9 gm 8.3 gm

EXAMPLE 9 A solution produced as described in Example 8 was kept at 70Cinstead of 60C. The yield of racemate after various time periods isshown in the following table:

lsomerization Ratio of Total active Yield of time (70C) isomersingredient racemate racemate: content of meso-form solution 0 days 0 10020.0 gm 2 days 33 67 I 17.6 gm 5.8 gm 5 days 48 52 15.6 gm 7.5 gm

:EXAMPLElO A solution of 50 gm of meso-triforine in 150 ml ofdimethylfor'mamide was heated to C for 4 hours, and the resultingbrownish solution was stirred into 1500 ml of water after cooling. Theprecipitate formed thereby was collected'by vacuum-filtration, washedwith water and dried at 60C. Yield: 47 gm (94% of the startingquantity). Ratio of racemate meso-form =41 59; i.e. a yield of racemateof 19.3 gm.

EXAMPLE 1 1 A mixture of 50 gm of meso-triforine and 100 ml ofN-methylpyrrolidone was heated to 95C for 3 16 hours. After cooling, theresulting solution was diluted with 1000 ml of water, and thecrystallizate was collected by vacuum filtration, washed with water anddried at 60C. 46 gm of amixture of isomers was obtained with a ratio ofracemate: meso-form 42.5 57.5, i.e. a yield of racemate of 19.5 gm.

EXAMPLE 12 A mixture of 46 gm of meso-triforine, 400 m1 of cyclohexanoneand 20 ml of water was heated to 95C for '8 hours, whereby amilky-turbid solution was formed.

The cyclohexanone was distilled off as far as possible, and the residuewas washed with water, vacuumfilte'red and extracted with 50 ml ofdimethylformamide at room temperature. The extracted filtrate wasdiluted with 500 ml of water, and the precipitate formed thereby wascollected by vacuum filtration, washed with-water and dried at 60C.

19 gm of triforine were obtained'with a ratio of racemate meso-form 7921, i.e. the yield of racemate amounted to 15.0 gm.

For agricultural plant protection purposes, the triforine isomersaccording to the present invention are incorporated as activeingredients into conventional agricultural plant protectioncompositions, that is, compositions consisting essentially of an inertsolid or liquid carrier an an effective plant-protecting, especiallyfungicidal amount of the active ingredient, such as dusting powders,granulates, wettable suspension powders, emulsion concentrates,'spraysand the like. The effective active ingredient concentration range inliquid forms of such compositions is 0.001 to 0.1 by weight,

. preferably 0.004 to 0.05% by weight, based on the total weight; inultra-low-volume compositions and dusting powders the active ingredientconcentration may also be higher (up to about 85% by weight).

The following examples illustrate a few agricultural plant protectioncompositions comprising an isomeric triforine of the present inventionas an active ingredient and represent the best modes contemplated ofputting the invention into practical use. The percentages arepercentages by weight unless otherwise specified.

EXAMPLE l3 Dusting powder The composition is compounded from thefollowing ingredients:

lsom eric triforine of the instant invention 1% Talcum 98% Methylcellulose 1% The ingredients are admixed, and the mixture is milled intoa homogeneous powder.

EXAMPLE 14 Wettable suspension powder lsomeric triforine of the instantinvention 25% Kaolin 55% Colloidal silicic acid Lignin Sulfonatc(dispersing agent) 9% Sodium tctrapropylenebenzene sulfonate (wettingagent) 1% The ingredients are admixed, the mixture is milled into ahomogeneous powder, and prior to use the powder is suspended in asufficient amount of water to make a sprayable aqueous suspension withan active ingredient content of 0.001 to 0.5%.

EXAMPLE l5 Aerosol spray The composition is compounded from thefollowing ingredients:

isomeric triforine of the instant invention 0.05% Sesame oil 0.10%N-methylpyrrolidone 10.00% Frigen propellants 89.85%

The ingredients are admixed and filled into aerosol spray cans in theconventional manner.

EXAMPLE 16 Solution concentrate EXAMPLE 17 Solution concentrate 35.1 mlof the 42.8% triforine solution in DMF obtained in Example 2 are admixedwith gm of the ethanolamine salt of dodecyl benzenesulfonic acid, 5 gmof 2-ethyl-3-octyl-ethanol and 12 ml of xylene. The mixture is dilutedwith N-methylpyrrolidone (about 36 ml) to 100 ml. A solution concentratewith a content of 15% w/v of isomeric triforine (ratio ofl II 84 16) isobtained, which can be diluted with water to the required concentrationfor use.

EXAMPLE 18 Solution concentrate 10 gm of the pure triforine isomer Iobtained in Example l are dissolved in 40 ml of DMF. 15 gm of theisopropylamine salt of dodecyl benzene sulfonic acid are added to thesolution and the mixture is thoroughly mixed and diluted withN-methylpyrrolidone to 100 ml. A solution concentrate is obtained with acontent of 10% w/v of the triforine isomer I. By diluting theconcentrate with water to the desired active ingredient concentration,and effective spray for use in plant protection is obtained.

While the present invention has been illustrated with the aid of certainspecific embodiments thereof, it will be readily apparent to othersskilled in the art that the invention is not limited to these particularembodiments, and that various changes and modifications may be madewithout departing from the spirit of the invention or the scope of theappended claims.

We claim:

1. Racemic triforine or a mixturethereof with mesotriforine, saidmixture consisting of at least 60% by weight of racemic triforine andthe balance mesotriforine.

2. The method of isolating racemic triforine or the said mixture ofclaim 1, which comprises the steps of extracting conventionally preparedtriforine containing about 50% by weight of racemic triforine with asolvent or solvent mixture wherein the solubility ratio of racemictriforine to meso-triforine is about 3:2, and isolating the extractedsubstance.

3. The method of claim 2, wherein said solvent mixture used forextraction is a mixture of acetone and water containing by volume ofwater.

4. The method of claim 2, wherein the solvent used for extraction isdimethylformamide.

5. The method of claim 2, wherein a deficient amount of said solvent orsolvent mixture for extraction is used such that practically only theracemic triforine is completely dissolved, while the major amount ofmeso-triforine remains undissolved.

UNITED STATES PATENT OFFICE CERTIFICATE 0 CORRECTION 0 Patent No.3,912,73 Dat October 11%, 1975 Inventor(s) WALTER 0ST, KLAUS THOMAS.EKTGEHARD AMADORI and ROLF DARS It is certified that error appears inthe above-identified patent and that said Letters Patent are herebycorrected as shown below:

' In Col. 10, line 59-"Sc" should read 80C In C0 1. 11, line 26-"-etnyl"should read -ethyl In Col. 12, line "-ehtyl" should read -ethy1 In Col.13, line A -"'+82.2"" should read -82.2

In Col. 18, line 19-- "and" should. read an M Signed and Scaled thistwenty-seventh D y f January 1976 [SEAL] Arrest:

RUTH c. MASON c. MARSHALL DANN Arresting Officer Commissioner oj'Patentsand Trademarks

1. RACEMIC TRIFORINE OR A MIXTURE THEREOF WITH MESO-TRIFORINE, SAIDMIXTURE CONSISTING OF AT LEAST 60% BY WEIGHT OF RACEMIC TRIFORINE ANDTHE BALANCE MESO-TRIFORINE.
 2. The method of isolating racemic triforineor the said mixture of claim 1, which comprises the steps of extractingconventionally prepared triforine containing about 50% by weight ofracemic triforine with a solvent or solvent mixture wherein thesolubility ratio of racemic triforine to meso-triforine is about 3:2,and isolating the extracted substance.
 3. The method of claim 2, whereinsaid solvent mixture used for extraction is a mixture of acetone andwater containing 90% by volume of water.
 4. The method of claim 2,wherein the solvent used for extraction is dimethylformamide.
 5. Themethod of claim 2, wherein a deficient amount of said solvent or solventmixture for extraction is used such that practically only the racemictriforine is completely dissolved, while the major amount ofmeso-triforine reamins undissolved.